1. Field of the Invention
The present invention relates to an image processing system and a color image processing apparatus for processing image signals by encrypting the signals.
2. Related Arts
Recently, as the performance of color copying machines has been improved, crimes of forging documents, such as paper monies or securities, by using these copying machines illegally have increased in number.
To prevent such crimes, a system has been studied in which data of image patterns representing documents, such as paper monies and securities, are registered in a copying machine itself beforehand, and an image identifying circuit identifies these registered data, thereby forcibly inhibiting illegal copying in accordance with the identification result. However, since the number of registrable image patterns is limited in a forgery preventing circuit of this type, it is impossible to register all available documents, such as paper monies and securities.
In addition, in the case of a color copying machine separable into a reader unit and a printer unit, even when a document consistent with a registered image pattern is to be copied, the circuit of the above sort cannot function if the original reader unit is replaced with another reader unit.
Also, connecting an unsuitable apparatus to the copying machine, even though it is not an illegal use as described above, lowers the signal level due to impedance mismatch between the two apparatuses, resulting in an adverse influence, such as an increase in noise of an image signal. This may interfere with the operation of the color copying machine main body and consequently introduce disadvantages to users.